On 2018年04月24日 18:48, David Sterba wrote: > On Tue, Apr 24, 2018 at 12:48:07PM +0800, Qu Wenruo wrote: >> Although we have already checked incompat flags manually before really >> mounting it, we could still enhance btrfs_check_super_valid() to check >> incompat flags for later write time super block validation check. > > But the calls are in reverse. First the validation is called and then > the incompat bits are verified if the filesystem is mountable. > > With change in this patch, any uknonwn incompat bit at mount time will > be reported as corruption. This does not make sense.
Oh sorry, I just though incompat flags is checked before calling
btrfs_validate_super().
>
> I've read the discussion under previous version again, IMHO the best way
> to report what's going on is to use 2 functions for mount ant pre-commit
> time.
OK, next version will go that direction.
Although it may still be a little tricky to split what we need in
btrfs_validate_super() and btrfs_precheck_super().
What about this idea:
- btrfs_precheck_super() only checks the very basis:
* magic
* incompat flags
* csum type
Any mismatch will do friendly prompt ("no btrfs detected" or
"unsupported flags/csum type" respectively)
- btrfs_validate_super() do the comprehensive check:
* Everything we did in this patchset
* including magic, incompat flags and csum type
Any mismatch will be considered as corruption.
For mount time, we call btrfs_precheck_super() then btrfs_validate_super().
For commit time, only btrfs_validate_super().
How about this solution?
Thanks,
Qu
>
> We can't expect that random user will understand that new unsupported
> flags actually mean corruption or that unsupported bits at mount time
> are not really a corruption.
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